Get language for a post

Hi!

I have planned to add the function below in v1.5.4

/*
 * returns the post language
 *
 * @since 1.5.4
 *
 * @param int $post_id
 * @param string $field optional the language field to return 'name', 'locale', defaults to 'slug'
 * @return bool|string the requested field for the post language, false if no language is associated to that post
 */
function pll_get_post_language($post_id, $field = 'slug') {
	global $polylang;
	return isset($polylang) && ($lang = $polylang->model->get_post_language($post_id)) ? $lang->$field : false;
}